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- Ara, Kazi Zubaida Gulshan, et al.
(författare)
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Engineering CGTase to improve synthesis of alkyl glycosides
- 2021
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Ingår i: Glycobiology. - : Oxford University Press (OUP). - 1460-2423. ; 31:5, s. 603-612
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Tidskriftsartikel (refereegranskat)abstract
- Alkyl glycoside surfactants with elongated carbohydrate chains are useful in different applications due to their improved biocompatibility. Cyclodextrin glucanotransferases can catalyse the elongation process through the coupling reaction. However, due to the presence of a hydrophobic tail, the interaction between an alkyl glycoside acceptor and the active site residues is weaker than the interaction with maltooligosaccharides at the corresponding site. Here we report the mutations of F197, G263 and E266 near the acceptor subsites in the CGTase CspCGT13 from Carboxydocella sp. The results showed that substitutions of both F197 and G263 were important for the binding of acceptor substrate dodecyl maltoside during coupling reaction. The double mutant F197Y/G263A showed enhanced coupling activity and displayed a 2-fold increase of the primary coupling product using γ-cyclodextrin as donor when compared to wildtype CspCGT13. Disproportionation activity was also reduced, which was also the case for another double mutant (F197Y/E266A) that however not showed the corresponding increase in coupling. A triple mutant F197Y/G263A/E266A maintained the increase in primary coupling product (1.8-fold increase) using dodecyl maltoside as acceptor, but disproportionation was approximately at the same level as in the double mutants. In addition, hydrolysis of starch was slightly increased by the F197Y and G263A substitutions, indicating that interactions at both positions influenced the selectivity between glycosyl and alkyl moieties.
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- Grey, Carl, et al.
(författare)
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Process development of oxygen-demanding reactions utilizing a simple design with parallel glass tube reactors - Evaluated using Gluconobacter oxydans (DSM 24525)
- 2012
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 30:5-6, s. 441-445
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the possibility of using simple glass tubes as reactors for oxygen-demanding reactions, a setup was assembled to study the initial rate of conversion of glycerol to dihydroxyacetone (DHA) using Gluconobacter oxydans. Several parallel 10 mL glass tubes were incubated in a temperature-controlled shaker. The concentration of DHA was determined using a fast spectrophotometric HPLC-based method that could process 3 samples/min. It was shown that the obtained results were reproducible and the reaction rates remained constant throughout the reaction. Further, the system reached a high volumetric activity of 15.48 g DHA L-1 h(-1) consuming 86 mmol L-1 h(-1) oxygen before the system became mass-transfer limited, indicating a high diffusion of oxygen. It was concluded that the reactor system is well suited for process development where the requirement for oxygen is high and that the assay developed can be used to determine the initial rate of DHA production.
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| 4. |
- Viloria-Cols, Maria, et al.
(författare)
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Agarose-coated anion exchanger prevents cell-adsorbent interactions
- 2004
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1043:2, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- A common problem during recovery of bioproducts by adsorption from particulate broths is fouling of the adsorbent material as a result of the interaction of cells and cell debris, which present negative charges, with the positively charged anion exchangers commonly used in bioprocesses. The effect of shielding an adsorbent with a layer of agarose on reducing the binding of cells while still allowing the low-molecular-mass bioproducts to be adsorbed was studied. Coating the anion-exchange resin Amberlite IRA-400 with agarose followed by cross-linking the agarose layer effectively prevented the binding of Escherichia coli, Saccharomyces cerevisiae, and Lactobacillus casei cells but allowed binding of lactic acid to the adsorbent. The cross-linked agarose layer was stable during recycling of the adsorbent. (C) 2004 Elsevier B.V. All rights reserved.
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